Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France.
Plant Cell. 2011 Feb;23(2):730-40. doi: 10.1105/tpc.110.081638. Epub 2011 Feb 4.
Following the endosymbiotic acquisition of mitochondria by eukaryotic cells, most of the genes in this organelle were transferred to the nucleus. To maintain mitochondrial biogenesis and function, nuclear and mitochondrial genomes require regulated and coordinated expression. In plant organelles, nuclear-encoded proteins targeted to the organelles control posttranscriptional and posttranslational mechanisms. Pentatricopeptide repeat (PPR) proteins are good candidates to play such regulatory roles. Here, we identify PNM1 (for PPR protein localized to the nucleus and mitochondria 1), a novel PPR protein that is dual localized to mitochondria and nuclei in Arabidopsis thaliana, as observed by green fluorescent protein fusions and immunodetection on subcellular fractions and on histological sections. Genetic complementation showed that loss of PNM1 function in mitochondria, but not in nuclei, is lethal for the embryo. In mitochondria, it is associated with polysomes and may play a role in translation. A genetic screen in yeast identified protein partners of PNM1. These partners, the nucleosome assembly protein NAP1, and the transcription factor TCP8 interact with PNM1 in the nucleus in planta. Furthermore, TCP8 can bind the promoter of PNM1. This suggests that PNM1 might be involved in the regulation of its own gene expression in the nucleus and could thus play a role in gene expression adjustments between mitochondria and the nucleus.
在真核细胞内共生获得线粒体之后，这个细胞器中的大多数基因都转移到了细胞核中。为了维持线粒体的生物发生和功能，核基因组和线粒体基因组需要受到调控和协调表达。在植物细胞器中，靶向细胞器的核编码蛋白控制转录后和翻译后机制。五肽重复（PPR）蛋白是发挥这种调节作用的良好候选物。在这里，我们鉴定了 PNM1（核和线粒体定位的 PPR 蛋白 1），一种新型 PPR 蛋白，在拟南芥中通过绿色荧光蛋白融合和亚细胞部分及组织切片的免疫检测观察到其双重定位于线粒体和细胞核。遗传互补表明，PNM1 在细胞器（而非细胞核）中的功能丧失对胚胎是致命的。在线粒体中，它与多核糖体相关联，可能在翻译中发挥作用。酵母中的遗传筛选鉴定了 PNM1 的蛋白伴侣。这些伴侣，核小体装配蛋白 NAP1 和转录因子 TCP8 在植物体内的细胞核中与 PNM1 相互作用。此外，TCP8 可以结合 PNM1 的启动子。这表明 PNM1 可能参与细胞核中自身基因表达的调控，从而可能在线粒体和细胞核之间的基因表达调节中发挥作用。
